Hybrid Cationic Ring Opening Reaction,preparation And Characterization Of Nanocomposites Based On Epoxy Resin

Owing to their relatively high mechanical propeties and prominent performance in adhesion,epoxy resins are widely used in aerospace,automobile industry,electronic engineering and coating areas.However,the choice of curing agent and determination of curing conditions have a great influence on the structure and properties of epoxy resin.In order to obtain the cured epoxy resin with excellent performance,the cationic open ring polymerization and hybrid nanocomposites based on epoxy resin were studied with iodonium salt as initiator.Two kinds cationic initiators diphenyliodonium fluoro phosphate(DPI·PF6)and diphenyliodonium fluoride-borate(DPI·BF4)were synthesized.The hybrid nanocomposite were prepared with polyhedral oligomeric silsesquioxane(POSS),carbon nanotubes(CNTs)and graphene as modifiers.The cationic hybrid curing mechanism and kinetics of epoxy resin were studied,the thermal properties,mechanical properties and microstructure of the hybrid cured materials were characterized.The main research contents are as following:(1)Two kinds of POSS-containing epoxy resin/unsaturated polyester hybrid UV cured membrane of MAP-POSS/UPR-ER and G-POSS/UPR/ER were prepared by using DPI·PF6as initiator.UV curing process of the two system,the properties and micromorphology of the film were analyzed by DSC,DMA,TGA and SEM.The results demonstrate that the thermal stability,mechanical properties and glass transition temperature(T_g)of the film were improved with the addition of POSS.The hydrophobicity of film surface is enhanced by the increase of the POSS ratio.(2)The hybrid cationic thermal polymerization of bisphenol-A epoxy resin(E51)using diphenyliodonium fluoride-borate(DPI·BF4)as initiator and BPO as co-initiator was investigated by DSC.POSS-containing organic-inorganic hybrid epoxy resin composites were obtained through free radical-cationic thermal curing of E51 epoxy resin with MAP-POSS or G-POSS.The curing process,mechanism and reaction kinetics were characterized,and thermal properties,dynamic mechanical properties of the composites were investigated.The results show that the initial thermal curing temperature of E51 system decreases and the cationic ring-opening average activation energy E_a increases by adding the G-POSS,but it is decreased with added MAP-POSS,because vinyl of MAP-POSS has a synergistic effect on free radical-cationic reaction.The hybrid cationic polymerization mechanism and curing kinetics of E51/MAP-POSS system could be simulated by the autocatalytic?esták-Berggren(S-B)model.The thermal stability enhanced,but the T_g increased first and then decreased with the increasing POSS content.(3)The G-POSS-containing nanocomposite film was prepared by hybrid cationic ring-opening polymerization from G-POSS and KH560 using DPI·BF4/BPO initiator system.The curing reaction kinetics,dynamical mechanical properties,thermal degradation properties and morphological structures of G-POSS/KH560 system were investigated.The results show that the curing reaction activation energy E_a decrease when KH560 is added into the reaction system,and the curing reaction kinetics can be simulated by the?esták-Berggren(S-B)model.Membrane surface of pure polymerized G-POSS has uniform distribution of less than 1.7 nm high protrusions.T_g and thermal stability of the system first increased and then decreased with the increasing KH560 content.(4)The bio-based gallic acid epoxy resin(GAER)was prepared from gallic acid(GAER)and epichlorohydrin in the existence of four butyl ammonium iodide,and mixed with glycidyl methacrylate(GMA)to form free radical-cationic hybrid curing system(GAER/GMA).Then the GAER/GMA/MWCNTs nanocomposites can be prepared by dispersing MWCNTs into GAER/GMA system using DPI·BF4 as a cationic initiator and BPO as co-initiator.The curing process of GAER/GMA,thermal properties,dynamic mechanical properties and microstructure of GAER/GMA/MWCNTs nanocomposites were investigated.The results showed that the GMA can play the role of promoting to GAER curing.The storage modulus,loss modulus and thermal stability of GAER/GMA/MWCNTs composites improved with increasing MWCNTs content,and T_g first increased and then decreased.The T_g of the nanocomposite with 0.5 wt%MWCNTs is 9.3~oC higher than that of the pure epoxy system.Compared with pure GAER/GMA system,the initial thermal degradation temperature increases 10~oC,and the thermal degradation E_a increases 68.6 k J/mol when the MWCNTs content is 1.0 wt%.MWCNTs are well-distributed in the epoxy system when its content is not over 1.0 wt%.Gallic acid epoxy monomer can be employed to functionalize CNTs via?-?interactions to inhibit their aggregation.(5)The fully oxidized graphite oxide(GO)was prepared by Hummers method,and reducing graphene(r-GO)was prepared by bio-based gallic acid(GA)as a green reducing agent,which avoided the use of toxic chemical reagent.The r-GO was characterized by FTIR and XRD,AFM,SEM,TEM and showed that the layer graphene had formed.The succinic anhydride(SUA)was used as a curing reagent,and the bio-based GAER/r-GO/SUA and GAER/GO/SUA glass fibre-reinforced nanocomposites were prepared and characterized.The results showed that the heat resistance of the composites increased,the tensile strength,impact strength and T_g showed the trend of the first increase and then decrease with increasing GO and r-GO content.Compared with bisphenol A type epoxy resin(E44),the impact strength of GAER is higher,but tensile strength is lower.Gallic acid epoxy resin has the application prospect in the field of instead bisphenol A type epoxy resin.These works provide the theoretical basis for the preparation of high performance POSS-containing epoxy resin nanocomposites by free radical-cationic hybrid curing mechanism.On the other hand,the increasingly serious oil crisis could be countered through synthesis and application of bio based epoxy resin by using renewable resources.In addition,these works also provide a new choice for the uniform dispersion of carbon nanotubes,green reduction of graphene and preparation of its nanocomposites.